initial commit, not beautiful but it works

.gitignore

@@ -0,0 +1 @@
+prepare-commit-msg

prepare-commit-msg.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"bytes"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+)
+
+func readFile(filename string) string {
+	contents, err := ioutil.ReadFile(filename)
+	if err != nil {
+		log.Printf("Error during reading file: %s", err)
+		return ""
+	}
+	return string(contents)
+}
+
+func main() {
+	cmd := exec.Command("git", "status", "-s")
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	err := cmd.Run()
+	if err != nil {
+		panic(err)
+	}
+
+	resultLines := strings.Split(out.String(), "\n")
+	if resultLines == nil {
+		return
+	}
+
+	re := regexp.MustCompile(`package\s(\w+)`)
+	names := make(map[string]bool)
+	for _, filenameStatus := range resultLines {
+		if filenameStatus != "" {
+			explodedStatus := strings.Split(strings.TrimSpace(filenameStatus), " ")
+			if len(explodedStatus) > 1 {
+				filename := explodedStatus[len(explodedStatus)-1]
+				status := explodedStatus[0]
+				if status == "??" {
+					continue
+				}
+
+				content := readFile(filename)
+
+				pkg := re.FindStringSubmatch(string(content))
+				if len(pkg) > 1 {
+					names[pkg[1]] = true
+				}
+
+			}
+		}
+	}
+
+	if len(names) > 0 {
+		prefix := "["
+		i := 0
+		for name, _ := range names {
+			if i > 0 {
+				prefix += "|"
+			}
+			prefix += name
+			i++
+		}
+		prefix += "] "
+		filename := os.Args[1]
+		msg := readFile(filename)
+		ioutil.WriteFile(filename, []byte(prefix+msg), 0x777)
+	}
+}